Operation Manual
FarSounder, Inc.
F31552 (Rev. 3.8.0)
Page 57 of 69
Figure A.2. Reflections from a medium angle
Figure A.3. Reflections from a shallow angle
In reality, the situation is actually quite a bit more complicated as the sound waves reflect not only off the
seafloor but also off the sea surface - sometimes more than once! (see figure A.4) This type of bouncing
is called multipath propagation.
Figure A.4. Multi-path reflections
Differing levels of sophistication enable various navigation sonar products to extract back-scatter reflections
from the seafloor at differing minimum echo levels. This directly defines the water depth limit at which a
particular sonar can produce bottom maps ahead of the vessel. As range increases, the angle at which
the incoming sound wave hits the seafloor becomes shallower. At some angle, not enough energy is
reflected back to the receiver to allow for sea bottom detection and mapping. The FarSounder-500 and
FarSounder-1000 products are specified as 8 water depth sonars. This means they can map the seafloor
out to a range equal to 8 times the depth below the transducer. Depending on the actual local propagation
conditions and the seafloor composition, this range may be longer or slightly shorter.
One of the most impressive features of FarSounder's technology is its shallow water capability. Though
FarSounder's products are specified as 8 Water Depth systems, 10+ Water Depth performance can
sometimes be achieved in certain conditions. However, even beyond their water depth capability,
FarSounder sonars are still able to detect objects out to farther ranges. This seems obvious for objects
